Page:Proceedings of the Royal Society of London Vol 1.djvu/442

Rh the chlorine is found to divide itself equally between the other two.

So also with respect to the relative afﬁnities of carbonic oxide for chlorine or for oxygen. The new gas is not decomposed by oxygen, neither is carbonic oxide altered by admixture with any proportion of chlorine that has been tried.

The eruption here described by Capt. Tillard was ﬁrst observed by him on the 12th of June, 181], having burst forth only two days before. It had been preceded by another eruption in the month of January, about three miles distant. Having come to anchor on the 13th in the road of Porto del Gerda, Capt. Tillard set off on the fol- lowing morning with some other gentlemen, for the purpose of witnessing the phenomena from the adjacent cliffs of St. Michael. The place of the eruption was scarcely a mile from the base of the cliff, which was nearly perpendicular, and about 400 feet‘ high.

In the most quiescent state of the volcano, there appeared a circular body of smoke over the surface of the water, in continual rotatory motion, extending itself to leeward; but suddenly a column of very black ashes and cinders would shoot up, in the form of a spire, inclined from ten to twenty degrees from the perpendicular; and, again, a second, third, and fourth column, each overtopping the preceding, till the last appeared more above the level of the eye than the sea was below it.

When the ﬁrst impetus that raised the column ceased, the smoke was seen to break into various fanciful forms ; some ascending by their proper levity, others carried downwards by the particles of falling ashes, so as to give the appearance of pendent plumes of black and white.

These bursts were always accompanied by vivid ﬂashes of lightning in the densest part, and followed by a succession of waterspouts that appeared drawn up by the masses of smoke as they rolled away before the wind.

The part of the sea where the volcano was situated was known to be full thirty fathoms deep; but in the course of the time that Capt. Tillard and his friends were watching it, a ridge was seen to project above the surface of the water; and before they quitted the cliﬂ“, which was in about three hours, a complete crater was formed, apparently 400 or 500 feet in width, and elevated on the leeward side not less than twenty feet in height.

The great eruptions were generally attended with sounds like the ﬁring of cannon or musquetry, and often with slight shocks of earthquake.

On the next day the volcano continued to emit clouds of black smoke and ashes, but was comparatively tranquil.